1. Field of the Invention
This invention relates to a flexible optical connecting part for optically connecting between circuit boards including optical elements and between optical component parts.
2. Description of the Related Art
An optical transmission technology is used in communication networks, since it is suitable for high-speed high-capacity transmission of information. Recently, it has been proposed to utilize the optical transmission technology in an optical communication system and the like. Major component parts of such a system include an optical connecting part comprised of optical fibers forming signal paths for connection between parts or between boards, flexible boards sandwiching the optical fibers, and optical connectors attached to foremost ends of the optical fibers, respectively. As an example of the above optical connecting part, there has conventionally been proposed an optical connecting part (optical mutual connection device) comprised of a lower flexible board (board having flexibility), optical fibers fixed to the lower flexible board using an adhesive (pressure sensitive adhesive), an upper flexible board (cover layer) covering the surface of the resulting sub-assembly, and optical connectors (optical fiber-terminating means, such as pairs of silicon chips having a V groove formed therein) attached to foremost ends of the optical fibers (see Publication of Japanese Patent No. 2574611).
In general, optical fibers are manually connected to each other via optical connectors. Due to the recent demand for miniaturization of optical and electronic devices, only a minimum space is left in such devices, which makes it difficult to perform the operation of connecting optical fibers, and therefore, there is a demand for softening portions of the optical connecting part close to the optical connectors so as to facilitate the connecting operation. It is possible to comply with such a demand by reducing the thicknesses of flexible boards and adhesive layers. However, if the thicknesses of the flexible boards and the adhesive layers are reduced, there is a fear that the optical fibers cannot be sufficiently protected, which makes it impossible to employ this method.